Process for manufacturing rigid polyisocyanurate foam products

ABSTRACT

A process for manufacturing an insulation board comprising a rigid polyisocyanurate foam core having two major surfaces and a facing material on at least one of the major surfaces, comprising (a) conveying a facing material along a production line for attachment to one major surface of the core; (b) applying a foam-forming mixture of polyisocyanurate to the facing material such that the mixture is applied along the entire width of the facing material; (c) optionally conveying a second facing material along the production line for attachment to the other major surface of the core; (d) conveying the facing material with applied foam-forming mixture into a laminator which comprises a gap for foam expansion and allowing the mixture to foam and expand to fill the gap within the laminator; and (e) curing the foam. The process provides excellent boardstock thickness control, minimal wasted densification at the foam/facer interface, greater compressive strength and high line speed.

FIELD OF THE INVENTION

The present invention relates to a process for manufacturing productscomprising rigid polyisocyanurate foam.

DESCRIPTION OF THE RELATED ART

The manufacture of flexible faced, rigid polyisocyanurate foaminsulation boardstock is commonly practiced by a process calledrestrained rise lamination. The restrained rise process relies on acombination of chemical component blending, precision metering, reactivecomponent mixing and dispensing, use of a moving opposed platen pressurelaminator, and use of dimensioning finishing equipment.

In the traditional restrained rise process, isocyanate ("Component A")is used as received. Component A is supplied by pump to a metering unit,or a metering pump. A premix ("Component B") containing polyol,expansion agent, catalyst and surfactant is prepared according to adefined formulation in a mix tank. Component B is also supplied by pumpto a metering unit, or a metering pump. The metering pumps boost thepressure generally to 2000 to 2500 psi and control the flow ofComponents A and B to a precise ratio as determined by the desiredchemistry. The pumps deliver Components A and B to at least one foammixhead. Inside the mixhead, the Components A and B are impinged againsteach other at high pressure, which results in intimate mixing of thecomponents.

The mixed chemicals exit the mixhead and are dispensed onto a movingbottom facing sheet in a plurality of discrete, liquid streams, in aquantity depending on the type and thickness of desired final boardstockproduct. The facing sheet carrying the chemical streams then enters apressure laminator. The spacing, or gap, between the top and bottomplatens of the laminator is set to approximately the final desiredthickness of boardstock. The laminator temperature is adjusted typicallyto about 120 to 150° F. to insure that no heat is lost from thereacting, exothermic chemical mix, and to insure that the facings adherewell to the rising foam.

The mixed chemicals begin to react in about 5 to 10 seconds followingmixing, expanding about 35 to 40 times in volume in the laminator andcompleting reaction in about 35 to 45 seconds. Laminator speed isadjusted to insure that complete reaction occurs within the pressuresection of the laminator. The reaction rate is adjusted by catalystmodification to optimize chemical mixture "flow." Flow is a property ofthe reacting, rising foam by which expansion is controlled in such amanner that the foam properly expands both upward and sideways to fullyfill the moving cavity defined by the laminator. This reactivityadjustment is essential to control both the overall properties of thefinal product and the cost of manufacture. Improper flow results in poorfoam cell geometry which can deteriorate physical, thermal andflammability properties, and causes excessive densification of foamlayers in contact with facings.

Rigid boardstock, with facing firmly attached, exits the laminator. Thisboardstock is trimmed to the desired final width and length. Finishedproduct is conveyed to packaging equipment.

Much of the art in the manufacture of polyisocyanurate takes place wherethe mixed chemical streams are laid onto the bottom facer prior toentering the laminator. It is necessary that the chemical streams beplaced and configured properly to insure that the potential negativeeffects of the rising foam (e.g., densification of foam at the facerinterface through sideways expansion) are minimized. Proper chemicalsystem catalysis is also essential to insure that the rising foam flowsproperly. Process line speed must be balanced with the foam reactivityso that flow is preserved and the finished boardstock has reachedsufficient hardness to be further processed.

When done properly, acceptable foam physical, thermal and flammabilityproperties are achieved. The density spread between core foam densityand the in-place density, or IPD, is minimized (core foam density isdefined as the measured density of the foam section of one half thethickness of the board taken from the center of the thickness; in-placedensity is defined as the total quantity of foam chemicals in a completesection of board including layers of surface densification and chemicalthat has been absorbed into the facers). Typical values for core foamdensity versus IPD for restrained rise process foam boardstock are 1.75lb/ft³ for core foam density and 1.95 lb/ft³ for IPD. However, imbalanceof laydown, catalyst and line speed can easily drive IPD well over 2.0lb/ft³.

Typical maximum line speed for a restrained rise process isapproximately 1.5 feet/min for each foot of laminator length. That is, a70 foot long laminator will produce acceptable quality boardstock at 105feet/min at minimal cost; a speed of 2.0 feet/min per foot of laminatorcan be achieved on certain products with catalyst modification andcareful attention to operating parameters. It is advantageous toincrease line speed, and therefore production capacities, to gain moreoutput from a given piece of equipment.

While mechanical limitations (i.e., finishing saws, conveyors andpackaging equipment) can be modified to accommodate higher line speedsby conventional means, maintenance of proper foam properties and costefficiencies present a more difficult problem. Increased line speedreduces the laminator dwell time (the time that the reacting foam isinside the pressure laminator) and must be altered to complete foamreaction more quickly. As the reaction time is reduce, chemical flow isalso altered resulting in a condition commonly known as "lock up." Whenflow is lost, excessive densification at the foam/facer interfaceoccurs, and cell geometry can be altered in a manner such that importantproperties, including compressive strength, dimensional stability, faceradhesion, insulation value and certain flammability characteristics, aredeteriorated. It is therefore advantageous to remove or reduce the needfor chemical flow as a component of the process.

Another known process for making flexible faced, rigid polyisocyanuratefoam insulation boardstock is the free rise process. In this process,chemical laydown or distribution is accomplished through the use of apair of matched, precision metering rolls. Chemicals are dispensed justupstream of the metering rolls. The gap between the rolls is adjusted toapproximately 1/35 to 1/40 of the desired finished thickness of theboardstock. This small gap causes the dispensed chemical to form a"chemical bank" against the metering roll, forcing the chemical tospread across the full width of the bottom facer. A thin layer of mixedfoam chemicals (approximately 1/35 to 1/40 of the desired finishedthickness of the boardstock) is uniformly spread between the top andbottom facers. This composite then moves into a heated oven where thefoam reaction is completed. Foam expands 35 to 40 times in volume andbecomes sufficiently rigid for further processing. Final foam thicknessis controlled by precision adjustment of the metering rolls. Nomechanical restraint is utilized for thickness control, as with therestrained-rise process.

The free rise process does not require chemical flow. Dispensed andmetered chemicals need only expand in the thickness dimension and not inthe width dimension since the original laydown already accomplishes fallwidth application. By removing the need for flow, catalyst adjustmentsare made only to achieve complete reaction at the desired line speedwithout the negative impact of "locking up" the foam system. The freerise process is capable of speeds in excess of 250 feet/min.

An additional benefit of the free rise process is that density controlis achieved within more efficient limits. Since sideways flow ofexpanding chemical does not occur, densification at the foam/facerinterface is minimized. Density spreads of 1.70 lb/ft³ for core foamdensity and 1.75 lb/ft³ for IPD are routinely achieved.

Although the free rise process presents several significant advantagesover the restrained rise process, there are some deficiencies of thefree rise process that preclude its use for roof insulation boardstockmanufacture. Since the free rise process does not utilize a mechanicalmeans to control product thickness but instead relies on precisionmetering of chemicals and consistent expansion ratio, thicknessvariability becomes increasingly exaggerated as overall boardstockthickness is increased, resulting in boardstock that is unacceptable forfield application. For example, thickness variation in a 4 inch productcan easily be +/- 0.25 inches, which is unacceptable for manyapplications. Additionally, typical roof insulation facers are notuniform enough in thickness to provide precision surfaces in themetering roll process. Facer thickness variations will be exaggerated by35 to 40 times in the final board. Lastly, the free rise process doesnot employ a mechanical means of foam width formation resulting inexcessive waste through edge trim losses. These losses increase as theproduct thickness increases.

In view of the disadvantages of the prior art processes, there is a needfor an improved process for the manufacture of flexible faced, rigidpolyisocyanurate foam insulation boardstock.

SUMMARY OF THE INVENTION

The present invention is directed to a process for the manufacture offlexible faced, rigid polyisocyanurate foam insulation boardstock whichprovides excellent boardstock thickness control, minimal wasteddensification at the foam/facer interface, improved product propertiesand high line speed.

Thus, in one aspect, the present invention provides a process formanufacturing an insulation board comprising a rigid polyisocyanuratefoam having two major surfaces and a facing material on at least one ofthe major surfaces, the method comprising:

(a) conveying a facing material along a production line for attachmentto one major surface of the foam;

(b) applying a foam-forming mixture of polyisocyanurate to the facingmaterial in a manner comprising spreading the mixture with a spreadingmeans in the direction of the width of the facing material;

(c) optionally conveying a second facing material along the productionline for attachment to the other major surface of the foam;

(d) conveying the facing material with applied foam-forming mixture intoa laminator which comprises a gap for foam expansion and allowing themixture to foam and expand to fill the gap within the laminator; and

(e) curing the foam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a production line used to conduct the processaccording to the invention for making flexible faced, rigidpolyisocyanurate foam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a process for the manufacture of flexiblefaced, rigid polyisocyanurate foam insulation boardstock. By theprocess, a foam-forming mixture of polyisocyanurate is applied to afacing material, spread in the direction of, and preferably along theentire width of the facing material, and the facing material withapplied foam-forming mixture is then conveyed into a laminator whichcomprises a gap for foam expansion. The mixture is allowed to foam andexpand to fill the gap within the laminator, and the foam is cured.Optionally, facing material is attached to both sides of the core ofpolyisocyanurate foam. Facing materials may include coated or uncoatedpaper, glass or other fiber mat, gypsum, oriented strandboard, orsynthetic sheet material.

An important feature of the present invention is that it eliminates theneed for "flow" of the foam-forming mixture of polyisocyanurate in thedirection of the product width. Application of the foam-forming mixtureover the entire width of the facing material contributes to the lack ofneed for flow. Such application is accomplished, for example, by use ofa metering device, such as a metering roll. The present inventionencompasses, however, any manner of applying the foam-forming mixturealong the entire width of the facing material.

Use of the proper catalyst system is another factor which contributes tothe lack of need for flow. Catalyst systems used in conventionalrestrained rise processes typically are binary or ternary blends oftertiary amine (e.g., PMDETA, TMR-30 or DMEA) and one or more potassiumorgano salts (e.g., potassium octoate and/or potassium acetate). In therestrained-rise process, the ratios of the catalysts are set to achievefast initiation of reaction ("cream" time) and proper placement of"string gel" time to ensure proper "chemical flow," and sufficientcompletion of reaction prior to the boardstock exiting the pressuresection of the laminator ("firm" time). Further discussion of restrainedrise catalyst systems can be found, e.g., in U.S. Pat. No. 5,252,625,which is incorporated herein by reference. Line speed is important inthe restrained rise process, since the catalyst system is designed toachieve the best flow and therefore the most efficient use of chemicals,yet it must yield foam sufficiently cured to be further processed afterleaving the laminator. Line speed is therefore limited since, ascatalyst is increased to complete cure more quickly, gel time is alsoreduced which reduces flow and increases product cost through excessivedensification.

By the present invention, on the other hand, the expanding chemicals donot need to move sideways to fill the full width of the facing materialbecause the foam-forming mixture is initially applied to the facingmaterial and spread at least partially to remove at least a portion ofthe gaps between streams in the machine direction, and preferably spreadalong that entire width, with minimal or no gaps remaining, as thefacing with foam-forming mixture thereon is conveyed to therestrained-rise laminator.

Larger amounts of catalyst can therefore be added to complete cure ofthe foam very quickly, once in the laminator. However, use of aspreading means, e.g., a metering roll will cause a hold up of chemicalsin front of the roll (i.e., a "chemical bank"). In such instances thecream time must be delayed to avoid expansion of the foam in thechemical bank. Even though additional catalyst can be added to cure thefoam faster in the laminator, such catalysts generally also decrease thecream time.

Accordingly, in comparison to the restrained rise process, catalystsystems used in the present invention generally provide a long creamtime, and slightly delayed string gel to provide only minimal chemicalflow, and a rapid cure or firm time. With the practice of the presentinvention, typical foam reactivities (e.g., measured upon exit from ahigh pressure foam mixhead) are a cream time of about 18-20 second, agel time of about 28-30 seconds, and a firm time less than about 35seconds. Catalyst may be provided in a supply containing the polyol("Component B"), and/or as a separate component ("trim component") foraddition to the foam-forming mixture.

Examples of catalyst systems which can be used in the present inventioninclude:

Catalyst A:

5.0 parts per hundred of polyol (pphp) of a solution of potassiumoctoate in diethylene glycol (15% potassium; Hexcem 977 from OMG)

Catalyst B:

0.5 pphp of a solution of potassium acetate in diethylene glycol (10%potassium;

Catalyst 1123 from OMG)

2.0 pphp Hexcem 977

4.0 pphp Curithane 52 (from Air Products)

Catalyst C:

1.25 pphp Hexcem 977

2.5 pphp Dabco TMR-2 (from Air Products)

In conventional restrained rise processes, chemical operatingtemperatures (e.g., measured at the exit from a high pressure foammixhead) are about 75-95° F. However, cream time is lessened by hightemperature. In accordance with the present invention, it is thereforedesirable to operate with colder chemicals to delay cream time, forexample in use with a metering roll. Preferred chemical operatingtemperatures in the present invention are about 60-75° F. Control ofchemical temperature is advantageously accomplished through the use ofefficient heat exchangers placed downstream of metering pumps and asclose as possible to foam mixheads, preferably sensing and maintainingprecise temperature control at the mixhead.

In conventional restrained rise processes, typical maximum line speedsare about 1.5 feet per minute (fpm) for each foot in length of thepressure section of the laminator. For example, a 70 feet long laminatoroptimally runs at about 105 fpm. Catalyst system adjustment with carefuldistribution of chemicals and use of smooth facings can extend thisrange to about 2.0 fpm per foot of laminator (e.g., a 70 foot laminatorwould run at about 140 fpm).

Since the present invention removes concerns for chemical flow, linespeeds are ultimately only limited by the ability to catalyze the foamin such a manner that the residence time (i.e., the time that the foamis in the pressure section of the laminator) is sufficient to provideenough firmness for further processing (e.g., cutting and packaging),and to ensure that no further expansion of the board occurs (postgrowth). In accordance with the present invention, use of a meteringroll and appropriate catalyst system can thus provide line speeds up toabout 2.5 fpm per foot of laminator (i.e., about 175 fpm for a 70 footlaminator).

Line speeds above 2.5 fpm per foot of laminator can be achieved withadditional, non-pressurized residence time to ensure that the surfacesof the board (i.e., the interface of facing with foam core) are curedsufficiently to bind the facings firmly in place. Addition of anon-restraining hot air circulating oven (i.e., a post-cure oven) at theexit of the laminator can be used to provide additional heated residencetime. Oven length can be equal, for example, to about the length of thepressure laminator. Line speeds of up to about 3.0-3.5 fpm per foot oflaminator can be achieved with this embodiment.

Typical laminator temperatures, measured on the platen surface, rangefrom about 110° F. for 4 inch thick board to about 160° F. for 1/2 inchthick board. A temperature of about 200-250° F. is preferred for thepost-cure oven, if present.

Since the present invention involves the use of a restrained riselaminator, maximum thickness variation of insulation board madeaccording to the invention is typically less than about +/-0.08 inches,most typically about +/-0.06 inches at all final product thickness.

In conventional restrained rise processes, core foam densities of thefinished insulation board typically range from 1.70 to 1.75 pounds percubic foot (pcf). In place density (IPD) is significantly higher due todensification at the foam/facer interface caused by sideways movement ofthe expanding chemicals (i.e., chemical flow). This densification isgreater with thinner product. Thus, a 1 inch thick board with a coredensity of 1.70 pcf will generally have an IPD of about 2.00 pcf; and a2 inch thick board with the same core density will have an IPD of about1.90 pcf, and a 4 inch thick board will have an IPD of about 1.85 pcf.These high IPD's do not contribute to the performance of the product,but add significant cost. The present invention employs a restrainedrise laminator which requires some "packing" (slight overfill of thelaminator) to function as a thickness control. Therefore, the presentinvention generally provides an IPD of about 1.75 to 1.85 pcf for a corefoam density of about 1.70 to 1.75 pcf, regardless of product thickness.The present invention is generally applicable for the manufacture of anyflexible faced, rigid polyisocyanurate foam insulation boardstockdescribed in the prior art.

In the manufacture of rigid polyisocyanurate foams, according to thepresent invention, two preformulated components are used, commonlycalled the A-component and the B-component. Typically, the A-componentcontains the isocyanate compound that must be reacted with the polyol ofthe B-component to form the foam, and the balance of the foam-formingingredients are distributed in these two components or in yet anothercomponent or components.

In the broadest aspects of the present invention, any organicpolyisocyanate can be employed in the preparation of the rigidpolyisocyanurate foams. The organic polyisocyanates which can be usedinclude aromatic, aliphatic and cycloaliphatic polyisocyanates andcombinations thereof. Such polyisocyanates are described, for example,in U.S. Pat. Nos. 4,795,763, 4,065,410, 3,401,180, 3,454,606, 3,152,162,3,492,330, 3,001,973, 3,394,164 and 3,124,605, all of which areincorporated herein by reference.

Representative of the polyisocyanates are the diisocyanates such asm-phenylene diisocyanate, toluene-2,4-diisocyanate,toluene-2,6-diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate,hexamethylene- 1,6-diisocyanate, tetramethylene- 1,4-diisocyanate,cyclohexane- 1,4-diisocyanate, hexahydrotoluene 2,4- and2,6-diisocyanate, naphthalene- 1,5-diisocyanate, diphenylmethane-4,4'-diisocyanate, 4,4'-diphenylenediisocyanate,3,3'-dimethoxy-4,4'-biphenyl-diisocyanate,3,3'-dimethyldiphenylmethane-4,4'-diisocyanate; the triisocyanates suchas 4,4',4'-triphenylmethane-triisocyanate, polymethylenepolyphenylisocyanate, toluene-2,4,6-triisocyanate; and the tetraisocyanates suchas 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate.

Prepolymers may also be employed in the preparation of the foams of thepresent invention. These prepolymers are prepared by reacting an excessof organic polyisocyanate or mixtures thereof with a minor amount of anactive hydrogen-containing compound as determined by the well-knownZerewitinoff test, as described by Kohler in "Journal of the AmericanChemical Society," 49, 3181(1927). These compounds and their methods ofpreparation are well known in the art. The use of any one specificactive hydrogen compound is not critical hereto, rather any suchcompound can be employed in the practice of the present invention.

Preferred isocyanates used according to the present invention includeMondur 489 (Bayer), Rubinate 1850 (ICI), Luprinate M70R (BASF) and Papi580 (Dow). Isocyanate indices greater than about 200 are preferred,particularly from about 225 to about 325. In addition to thepolyisocyanate, the foam-forming formulation also contains an organiccompound containing at least 1.8 or more isocyanate-reactive groups permolecule. Preferred isocyanate-reactive compounds are the polyester andpolyether polyols. Such polyester and polyether polyols are described,for example, in U.S. Pat. No. 4,795,763.

The polyester polyols useful in the invention can be prepared by knownprocedures from a polycarboxylic acid or acid derivative, such as ananhydride or ester of the polycarboxylic acid, and a polyhydric alcohol.The acids and/or the alcohols may be used as mixtures of two or morecompounds in the preparation of the polyester polyols.

The polycarboxylic acid component, which is preferably dibasic, may bealiphatic, cycloaliphatic, aromatic and/or heterocyclic and mayoptionally be substituted, for example, by halogen atoms, and/or may beunsaturated. Examples of suitable carboxylic acids and derivativesthereof for the preparation of the polyester polyols include: oxalicacid; malonic acid; succinic acid; glutaric acid; adipic acid; pimelicacid; suberic acid; azelaic acid; sebacic acid; phthalic acid;isophthalic acid; trimellitic acid; terephthalic acid; phthalic acidanhydride; tetrahydrophthalic acid anhydride; pyromellitic dianhydride;hexahydrophthalic acid anhydride; tetrachlorophthalic acid anhydride;endomethylene tetrahydrophthalic acid anhydride; glutaric acidanhydride; maleic acid; maleic acid anhydride; fumaric acid; dibasic andtribasic unsaturated fatty acids optionally mixed with monobasicunsaturated fatty acids, such as oleic acid; terephthalic acid dimethylester and terephthalic acid-bis-glycol ester.

Any suitable polyhydric alcohol may be used in preparing the polyesterpolyols. The polyols can be aliphatic, cycloaliphatic, aromatic and/orheterocyclic, and are preferably selected from the group consisting ofdiols, triols and tetrols. Aliphatic dihydric alcohols having no morethan about 20 carbon atoms are highly satisfactory. The polyolsoptionally may include substituents which are inert in the reaction, forexample, chlorine and bromine substituents, and/or may be unsaturated.Suitable amino alcohols, such as, for example, monoethanolamine,diethanolamine, triethanolamine, or the like may also be used. Moreover,the polycarboxylic acid(s) may be condensed with a mixture of polyhydricalcohols and amino alcohols.

Examples of suitable polyhydric alcohols include: ethylene glycol;propylene glycol-(1,2) and -(1,3); butylene glycol-(1,4) and -(2,3);hexane diol-(1,6); octane diol-(1,8); neopentyl glycol;1,4-bishydroxymethyl cyclohexane; 2-methyl-1,3-propane diol; glycerin;trimethylolpropane; trimethylolethane; hexane triol-(1,2,6); butanetriol-(1,2,4); pentaerythritol; quinitol; mannitol; sorbitol; formitol;α-methyl-glucoside; diethylene glycol; triethylene glycol; tetraethyleneglycol and higher polyethyleneglycols; dipropylene glycol and higherpolypropylene glycols as well as dibutylene glycol andhigherpolybutylene glycols. Especially suitable polyols are oxyalkyleneglycols, such as diethylene glycol, dipropylene glycol, triethyleneglycol, tripropylene glycol, tetraethylene glycol, tetrapropyleneglycol, trimethylene glycol and tetramethylene glycol.

Particularly preferred polyester polyols include Stepanpol PS2352(Stepan) and Terate 2541 (Hoechst Celanese). Preferred amounts of thepolyester polyols are consistent with isocyanate indices greater than200, preferably between about 225 and 325.

Polyether polyols useful according to the present invention include thereaction products of a polyfunctional active hydrogen initiator and amonomeric unit such as ethylene oxide, propylene oxide, butylene oxideand mixtures thereof, preferably propylene oxide, ethylene oxide ormixed propylene oxide and ethylene oxide. The polyfunctional activehydrogen initiator preferably has a functionality of 2-8, and morepreferably has a functionality of 3 or greater (e.g., 4-8).

A wide variety of initiators may be alkoxylated to form useful polyetherpolyols. Thus, for example, poly-functional amines and alcohols of thefollowing type may be alkoxylated: monoethanolamine, diethanolamine,triethanolamine, ethylene glycol, polyethylene glycol, propylene glycol,hexanetriol, polypropylene glycol, glycerine, sorbitol,trimethylolpropane, pentaerythritol, sucrose and other carbohydrates.Such amines or alcohols may be reacted with the alkylene oxide(s) usingtechniques known to those skilled in the art. The hydroxyl number whichis desired for the finished polyol would determine the amount ofalkylene oxide used to react with the initiator. The polyether polyolmay be prepared by reacting the initiator with a single alkylene oxide,or with two or more alkylene oxides added sequentially to give a blockpolymer chain or at once to achieve a random distribution of suchalkylene oxides. Polyol blends such as a mixture of high molecularweight polyether polyols with lower molecular weight polyether polyolscan also be employed.

Any suitable blowing agent can be employed in the foam compositions ofthe present invention. In general, these blowing agents are liquidshaving a boiling point between minus 50° C. and plus 100° C. andpreferably between 0° C. and 50° C. The preferred liquids arehydrocarbons or halohydrocarbons such as chlorinated and fluorinatedhydrocarbons. Suitable blowing agents include HCFC-141b(1-chloro-1,1-difluoroethane), HCFC-22 (monochlorodifluoromethane),HFC-245 fa (1,1,1,3,3-pentafluoropropane), HFC-134a(1,1,1,2-tetrafluoroethane), HFC-365mfc (1,1,1,3,3-pentafluorobutane),cyclopentane, normal pentane, isopentane, LBL-2(2-chloropropane),trichlorofluoromethane, CCl₂ FCClF₂, CCl₂ FCHF₂, trifluorochloropropane,1-fluoro-1,1-dichloroethane, 1,1,1-trifluoro-2,2-dichloroethane,methylene chloride, diethylether, isopropyl ether, methyl formate,carbon dioxide and mixtures thereof.

The foams also can be produced using a froth-foaming method, such as theone disclosed in U.S. Pat. No. 4,572,865. In this method, the frothingagent can be any material which is inert to the reactive ingredients andis easily vaporized at atmospheric pressure. The frothing agentadvantageously has an atmospheric boiling point of -50° to 10° C., andincludes carbon dioxide, dichlorodifluoromethane, monochlorodifluoromethane, trifluoromethane, monochlorotrifluoromethane,monochloropentafluoroethane, vinylfluoride, vinylidenefluoride,1,1-difluoroethane, 1,1,1-trichlorodifluoroethane, and the like. Ahigher boiling blowing agent is desirably used in conjunction with thefrothing agent. The blowing agent is a gaseous material at the reactiontemperature and advantageously has an atmospheric boiling point rangingfrom about 10° to 80° C. Suitable blowing agents includetrichloromonofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane,acetone, pentane, and the like. In the froth-foaming method, the foamingagents, e.g., trichlorofluoromethane blowing agent or combinedtrichlorofluoromethane blowing agent and dichlorodifluoromethanefrothing agent, are employed in an amount sufficient to give theresultant cured foam the desired bulk density which is generally between0.5 and 10, preferably between 1 and 5, and most preferably between 1.5and 2.5, pounds per cubic foot.

The foaming agents generally comprise from 1 to 30, and preferablycomprise from 5 to 20 weight percent of the composition. When a foamingagent has a boiling point at or below ambient, it is maintained underpressure until mixed with the other components. Alternatively, it can bemaintained at subambient temperatures until mixed with the othercomponents. Mixtures of foaming agents can be employed.

Any suitable surfactant can be employed in the foams of this invention,including silicone/ethylene oxide/propylene oxide copolymers. Examplesof surfactants useful in the present invention include, among others,polydimethylsiloxane-polyoxyalkylene block copolymers available fromWitco Corporation under the trade names "L-5420", "L-5340", and Y10744;from Air Products under the trade name "DC-193"; from Goldschmidt underthe name, Tegostab B84PI; and Dabco DC9141. Other suitable surfactantsare those described in U.S. Pat. Nos. 4,365,024 and 4,529,745.Generally, the surfactant comprises from about 0.05 to 10, andpreferably from 0.1 to 6, weight percent of the foam-formingcomposition.

Facings for use in the present invention include any flat, sheetmaterial suitable to the required end application of the final boardproduct. At least the upper facer must be flexible enough to be wrappedtightly around a metering roll. Facers must also be flat enough to notsignificantly alter the small gap between metering rolls. Such materialsinclude aluminum foil/kraft paper laminations, bare aluminum foil, paperroof insulation facings, and coated glass fiber mats. A facer, as usedherein, may also include oriented strandboard or gypsum, in which casesuch rigid material is conveyed to the laminator, and foam-formingmixture is preferably applied directly thereon.

The examples below illustrate typical experimental protocols which canbe used to manufacture flexible faced, rigid polyisocyanurate foaminsulation boardstock according to the present invention. Such examplesare provided by way of illustration and not by way of limitation.

EXAMPLES

The following example describes application of the present invention,including the metering roll embodiment:

A chemical premix (Component B) was prepared in the batch tank to thefollowing formulation:

    ______________________________________                                        Terate 2541 polyol                                                                              100.00 pbw                                                    Hexcem 977 catalyst          0.62                                             Dabco TMR-2 catalyst         1.25                                             Tegostab B84PI surfactant    2.00                                             Water                        0.50                                             HCFC-141b                    36.00                                          ______________________________________                                    

The catalyst added to Component B was half of the required quantity. Theremaining catalyst was added as a separate component or "trim"component.

A catalyst blend (Component C or "trim component") was prepared to thefollowing formulation and placed in the Component C supply tank:

Hexcem 977 0.62 pbw

Dabco TMR-21.25

Component A is Rubinate 1850 isocyanate as received.

Components A and B were pumped in metered quantities (ratio of A:Bmaintained at 1.23:1 ) at pressures of about 2000 psi to a high pressureimpingement foam mixhead. Component C was metered at high pressure(about 2500 psi) and injected into the Component B stream immediatelyupstream of the mixhead. Level was adjusted to achieve desiredreactivity.

The foam forming mixture was deposited onto the bottom facing sheetimmediately before the metering rolls. The gap between the meteringrolls was adjusted to about 1/35th of the final desired thickness of theboard being manufactured. In this example, 1.0 inch residentialsheathing was being made and the gap was set to 0.029 inches between thefacers. Chemical component temperatures were adjusted to 65-70° F. A"bank" of mixed chemicals was created against the metering roll gapextending the full width (48 inches) of the final product. Laminatortemperature was adjusted to about 150° F.

Line speed was increased to the point where full product thickness andwidth were achieved. Speed settled in at about 120 fpm. Usingconventional restrained rise processing techniques, line speed wouldhave been about 110 fpm. Board was very firm with excellent flatness andfacer adhesion.

Densities were measured on the product from this production trial. Corefoam density was found to be 1.74 pcf and IPD was 1.82 pcf (standardproduct has a core foam density of about 1.70 pcf with an IPD of about1.90 pcf). Compressive strength was measured at 34 psi (standard productmeasures 18-20 psi). This represents a significant improvement. Allother physical and thermal properties were found to be equivalent toproduct manufactured by conventional means.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

We claim:
 1. A process for manufacturing an insulation board comprisinga rigid polyisocyanurate foam having two major surfaces and a facingmaterial on at least one of the major surfaces, the methodcomprising:(a) conveying a facing material along a production line forattachment to one major surface of the foam; (b) applying a foam-formingmixture of polyisocyanurate to the facing material in a mannercomprising spreading the mixture with a spreading means in the directionof the width of the facing material; (c) optionally conveying a secondfacing material along the production line for attachment to the othermajor surface of the foam; (d) conveying the facing material withapplied foam-forming mixture into a restrained rise laminator whichcomprises a gap for foam expansion and allowing the mixture to foam andexpand to fill the gap within the laminator; and (e) curing the foam. 2.The process according to claim 1 wherein the foam-forming mixture isspread along the entire width of the facing material.
 3. The processaccording to claim 1, wherein temperature of the foam-forming mixture isadjusted prior to application to the facing material.
 4. The processaccording to claim 1, wherein temperature of the foam-forming mixture iscontrolled by passing at least part of the components to be mixedthrough a heat exchanger prior to application to the facing material. 5.The process according to claim 1, wherein the line speed is at least 2.0feet/min per foot of laminator.
 6. The process according to claim 1,wherein the line speed ranges from about 2.0 to about 2.5 feet/min perfoot of laminator.
 7. The process according to claim 1, wherein theinsulation board is conveyed through a post-cure oven after exiting thelaminator.
 8. The process according to claim 1, wherein the line speedranges from about 2.5 to about 3.0 feet/min per foot of laminator. 9.The process according to claim 1, wherein the line speed ranges fromabout 3.0 to about 3.5 feet/min per foot of laminator.
 10. The processaccording to claim 1 which produces insulation board having a core foamdensity ranging from about 1.70 to about 1.75 lb/ft³ and an in-placedensity ranging from about 1.75 to about 1.85 lb/ft³.
 11. The processaccording to claim 1, wherein the cured insulation board varies inthickness by no more than +/-0.080 inches.
 12. The process according toclaim 1, wherein a metering device is used to apply the foam-formingmixture to the facing material.
 13. The process according to claim 12,wherein the metering device is a set of metering rolls.
 14. The processaccording to claim 1, wherein the foam-forming mixture comprises apolyisocyanate and a polyester polyol.
 15. The process according toclaim 1, wherein the foam-forming mixture comprises a polyisocyanate anda polyether polyol.
 16. The process according to claim 1, wherein thefoam-forming mixture is applied at a temperature ranging from about 60to 75° F.
 17. The process according to claim 1, wherein the temperatureof the foam-forming mixture is controlled by a heat exchanger downstreamof at least one metering pump supplying foam-forming mixture components,prior to application to the facing material.
 18. The process accordingto claim 1, wherein the rigid foam has a compressible strength greaterthan 20 psi.
 19. The process according to claim 1, wherein the rigidfoam has a compressive strength greater than 28 psi.
 20. The processaccording to claim 18, wherein the rigid foam has an in-place densityless than about 1.90 pcf.